I did think about Creationism when I put the dinosaur in there. After all, Middle-Earth was created, and there are canonically "dinosaur-like" creatures there (the Nazguls' steeds); so it seems logical Morgoth made them. Unless it was Yavanna.

I'm fairly certain Tolkien himself wasn't a Creationist though, although I did see a comment on a Tolkien forum once by someone assuming he must have been...

I'm fairly sure Tolkien would today be classified as a proponent of "intelligent design"... that evolution exists and the universe may be millions of years old, but that it was all created, set in motion, and maintained by God.

Gollum is an example of Tolkien's belief in evolution through adaptation. He also mentioned in one of his letters that the Nazguls' flying mounts were inspired by pterodactyls.

You can assume that Melkor just got tired of seeing his dinosaurs get run down by Oromë and decided to fit them with wings and fiery breath.

Hmm. As I hear it used, "intelligent design" is more than what you've described. It's the belief that God intervenes personally and specifically in each new species as it emerges; basically it's a rejection of the idea of natural selection entirely.

What you've described sounds to me more like 'theistic evolution': the idea that sure, it was God who set up the process in the first place, but now it works by itself according to natural law.

Tolkien was a conservative Christian, but in the 20th century British way. He didn't reject science and rationalism. in fact, something I only learned recently is that in the 1950s he thought about completely revising the Silmarillion mythology to bring it closer in line to real-life physics and biology: get rid of the flat earth, the stars being made later on in creation, and so forth. Probably luckily, he never finished the project (it would have meant changing far too many aspects of his stories) and Christopher Tolkien didn't include any mention of that when he edited the Silmarillion for publication.